The Physiology of Stress Chapter 2

“To understand the stress response, we must process a fundamental knowledge not only of psychology but of physiology as well.” —George Everly

The Physiology of Stress A series of neural and chemical reactions meant for physical survival If you can begin to understand the physiology of stress, then you can begin to use this knowledge to augment your own health and well-being in terms of techniques like mental imagery, biofeedback, diaphragmatic breathing, etc.

The Physiology of Stress (continued) Hans Selye, considered by many as the father of the study of stress, developed the idea that a direct relationship exists between chronic stress and excessive wear and tear throughout the body.

Psychophysiology Psychophysiology is a term to describe the body’s physiological reaction to perceived stressors suggesting that the stress response is a mind-body phenomenon.

The Human Brain Divided into three levels: 1. The vegetative level Autonomic responses (e.g., breathing, heart rate, etc.) 2. The limbic system Emotional thought processing 3. The neocortical level Human consciousness (rational thought processing)

The Nervous System Can Be Divided Into: The central nervous system (CNS) brain spinal cord The peripheral nervous system (PNS) consists of all neural pathways to the extremities

The Vegetative Level The lowest level of the brain is comprised of the: reticular formation brain stem

Reticular Activating System (RAS) The RAS is the link connecting the brain to the spinal cord. Several stress physiologists believe that this is the bridge joining the mind and the body as one. This organ functions as a communica-tion link between the mind and the body.

The Brain Stem The brain stem, comprised of the pons, medulla oblongata, and mesencephalon, is responsible for involuntary functions of the human body such as: heartbeat respiration vasomotor activity

The Limbic System The limbic system is the emotional control center and comprised of the: thalamus hypothalamus pituitary gland (also known as the master endocrine gland) These three glands work in unison to maintain a level of homeostasis

The Neocortical Level The neocortex is the highest level of the brain. It is at this level that sensory information is processed as a threat or a non-threat and where cognition takes place. This higher level of the brain can override a lower level and can influence emotional responses.

Physiological Systems Involved in the Stress Response The nervous system The endocrine system The immune system

The Autonomic Nervous System (ANS) The ANS regulates visceral activities and vital organs, including: circulation digestion respiration temperature regulation

Two Branches of the ANS That Act to Maintain Homeostatic Balance Sympathetic Nervous System Parasympathetic Nervous System

Sympathetic Nervous System Is responsible for the responses associated with the fight-or-flight response This physical arousal is stimulated through the release of catecholamines epinephrine (adrenaline) norepinephrine (noradrenaline)

Parasympathetic Nervous System Maintains homeostasis through the release of acetylcholine (ACh) Is responsible for energy conservation and relaxation

The Endocrine System Consists of a series of hormonal glands located throughout the body which regulate metabolic functions that require endurance rather than speed The endocrine system is a network of four components: glands, hormones, circulation, and target organs

The Endocrine System (continued) The glands most closely involved with the stress response are the: pituitary thyroid adrenal

The Nervous System and the Endocrine System Join together to form metabolic pathways or axis There are three pathways: the ACTH axis the vasopressin axis the thyroxine axis

The ACTH Pathways

Three Stages of Effects Associated with the Stress Response Immediate effects of stress Intermediate effects of stress Prolonged effects of stress

Immediate Effects of Stress Sympathetic nervous response Epinephrine and norepinephrine released Time: 2 to 3 seconds Like a phone call or instant message

Intermediate Effects of Stress Adrenal response Epinephrine and norepinephrine release from adrenal medulla Time: 20 to 30 seconds Like an email

Prolonged Effects of Stress ACTH, vasopressin, and thyroxine affect various metabolic processes Time: minutes, hours, days, or weeks Like an “overnight delivery”

Immediate, Intermediate, and Prolonged Effects of Stress Phone call Email Overnight delivery

Other Stress-Related Hormones DHEA Serotonin Melatonin

A Decade of Brain Research (1992–2002) Use of MRIs to measure conscious thoughts Repeated exposure to cortisol increases aging process of brain Repeated exposure to cortisol damages/ shrinks brain tissue Damage due to repeated exposure to cortisol appears to be irreversible We are “wired for stress” for physical threats yet all threats set the alarm

Insomnia and Brain Physiology Various neurochemicals are released in the brain during episodes of stress that can greatly affect one’s quality of sleep. The brain chemistry equation for sleep involves many neurochemicals including a delicate balance between seratonin and melatonin.

Insomnia and Brain Physiology (continued) As daylight decreases, melatonin levels increase to help promote sleep. Various factors affect seratonin levels, including light, food chemistry (carbohydrates), pharmaceutical use, and emotional stress, which in turn affect melatonin levels and hence the quality of sleep.

Study Guide Questions 1. What role does the nervous system play in the stress response? 2. What role does the endocrine system play in the stress response? 3. Name the three pathways (axes) of stress physiology. 4. What does new brain imaging tell us about stress physiology?